intel/genxml: Ignore tail leading/trailing whitespace in node_validator()

intel/genxml: Ignore tail leading/trailing whitespace in node_validator()

When importing or flattening genxml with the genxml_import.py script
in MR !20593, it can lead to the tail portion of xml items differing
in whitespace.

If we strip the trailing and leading whitespace from the tail string,
and the strings are equivalent, then we can consider the xml items to
be equivalent.

Signed-off-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Lionel Landwerlin <lionel.g.landwerlin@intel.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/24903>